Willie Nelson and Waylon Jennings are not only two of the greatest artists in country music history, but frequent collaborators and good friends. The two country legends remained close throughout the years, up until Jennings' death in 2002.

For their 1978 duet album titled Waylon & Willie, Nelson and Jennings recorded their version of an Ed Bruce tune called "Mammas Don't Let Your Babies Grow Up to Be Cowboys." The duo turned the song into a chart-topping success, and it spent a total of four weeks at number one on the Billboard country chart.

In 1979, Nelson and Jennings won the Grammy Award for Best Country Performance by a Duo or Group with Vocal for their performance of the song. It remains a beloved country classic, and the members of the Western Writers of America named it as one of the Top 100 Western Songs of All Time.

The duo teamed up to perform the song yet again during the 1986 Farm Aid Concert. Farm Aid is an annual benefit concert that was co-founded by Nelson with the intent of helping to raise funds for family farmers.

Nelson started off on stage alone before he invited Jennings to come out and join him. The crowd started roaring the second Jennings started singing, excited to hear him sing the classic song live. Eventually, Nelson joined in as well, and the duo ended up delivering a fun-filled performance that drove the crowd wild.

You can watch Nelson and Jennings sing "Mammas Don't Let Your Babies Grow Up to Be Cowboys" in the video below.